The use of mobile phones and personal digital assistants (PDA's) is becoming more and more common in everyday life. That is, more and more people from every walk of life are using mobile phones and PDA's for business and/or pleasure, out of necessity or just for common convenience. In fact, due to the now ubiquitous nature of mobile phone and PDA usage, it is just as common for persons to carry his/her mobile phone and/or PDA as it is to carry a wallet or purse. Indeed, in some quarters it is becoming more common for persons to carry only a mobile phone and/or a PDA since these devices are becoming capable of performing more and more functions and offering more and more services. For example, mobile phones are now capable of providing Internet access and PDA's are now capable of sending and receiving electronic mail.
As the world becomes more and more reliant on digital communications and systems, it is expected that mobile phones and PDA's will become more and more useful. For example, the use of personal identification number (PIN) codes are becoming more and more common for verifying the identity of a user of a digital system such as, for example, a bank automatic teller machine (ATM). As more and more digital systems adopt the use of PIN codes for identity verification, the number of PIN codes that a user of these digital systems must remember increases, particularly since it is often recommended for security purposes that users use different PIN codes for different digital systems. As a result of this increase in the number of PIN codes that must be remembered, some users of mobile phones and PDA's have begun to store their PIN codes in digital read/write memory which is now incorporated within most of these devices. That is, some users of mobile phones and PDA's have begun storing their PIN codes in the digital read/write memory that is now incorporated within their mobile phones and PDA's, rather than trying to memorize all of the increasing number of PIN codes that must be used to gain access to a corresponding increasing number of digital systems.
Despite the apparent benefit of storing PIN codes in the digital read/write memory of mobile phones or PDA's, a security problem exists with this practice. That is, the digital read/write memory in existing mobile phones and PDA's is not capable of preventing unauthorized users from accessing PIN codes stored therein. The only way that PIN codes, or any other data, that are stored within the digital read/write memory of a mobile phone or PDA are truly secure is if the digital read/write memory can withstand four basic types of attack. Namely, these four basic types of attack include: 1.) when an attacker cannot read the content of the memory and does not know (before the attack) anything that has been stored in the memory; 2.) when an attacker can read the content of the memory but does not know (before the attack) anything that has been stored in the memory; 3.) when an attacker cannot read the content of the memory but does know (before the attack) at least one thing that has been stored in the memory; and 4.) when an attacker can read the content of the memory and does know at least one thing that has been stored in the memory. Thus, for PIN codes, or any other data, that are stored within the digital read/write memory of a mobile phone or PDA to be truly safe and secure, the memory has to be resistant to all the different types of attacks listed above.
In view of the foregoing, it would be desirable to provide a technique for securely storing data within a memory which overcomes the above-described inadequacies and shortcomings while also withstanding all of the above-described types of attacks.